The present invention relates generally to article wrapping apparatus and, in a preferred embodiment thereof, provides improved apparatus and methods for sealing and cutting apart spaced longitudinal sections of a wrapping material tube exiting, for example, a horizontal wrapping machine to form individual, sealed packages each containing one or more articles previously loaded thereinto by an article infeed portion of the machine.
Horizontal wrapping machines of various types are well known in the material handling art and typically comprise a forming box structure through which an elongated sheet of flexible wrapping material is drawn. The forming box is operative to continuously form from the sheet a forwardly moving tube having a rearwardly disposed open inlet end, and a laterally outwardly projecting "fin" defined by drawn-together side edge portions of the sheet. An article infeed system is used to sequentially insert articles to be wrapped into the open tube inlet end. The inserted articles, in a longitudinally spaced array, are then carried within the wrapping material tube as it forwardly exits the forming box. The individual articles (or associated groups of articles, as the case may be) forwardly transported within the tube are spaced apart by spaced longitudinal sections of the tube.
As the article-containing tube exits the forming box, its fin portion is drawn between, and heat sealed, by an opposed pair of counter-rotating heat sealing wheels. The sealed fin is then passed through a foldover station which operates to fold the sealed fin over onto an adjacent portion of the tube. The tube, with its sealed and folded-over fin, is then passed through a cutting and sealing station which operates to compress, heat seal and transversely cut the longitudinal tube sections between longitudinally adjacent article pairs or sets to form individual, article-containing packages with sealed opposite ends.
In conventional wrapping machines, this final sealing and cutting process is typically performed by passing the tube through a pair of opposed, counter-rotating cutting and sealing bar structures which intermittently mesh at radially outer ends thereof to simultaneously compress, heat seal and cut each longitudinal tube section as it passes through the cutting and sealing station. To effect this process, one of the intermittently meshing outer bar ends is provided with a cutting knife interposed between first and second corrugated heat sealing sections, while the other end of the other bar is provided with an anvil portion interposed between first and second corrugated heat sealing sections which are mirror images of the corresponding corrugations on the knife-carrying bar.
As a given longitudinal tube section passes between the rotating bars, the outer bar ends cooperate to sequentially mesh their first corrugated sections to form a corrugated heat seal along a lead portion of the tube section, force the cutting knife through the tube section and against the anvil to cut away the heat sealed tube section from the balance of the tube section, and then mesh the second corrugated bar end portions to form a corrugated heat seal along the balance of the longitudinal tube section.
In many conventional wrapping machines, the outer ends of these combination sealing and cutting bars are configured in a manner such that the ridges and valleys of the corrugated heat seal areas at the opposite ends of the resulting packages extend parallel to the lengths thereof (i.e., transversely to the end cut lines). Due to the relatively high linear travel rate of the wrapping material tube through the cutting and sealing station of the wrapping machine, the outer sealing and cutting bar ends operatively contact the spaced longitudinal bag sections only for a brief instant. Accordingly, it is not an uncommon occurrence for imperfect seals to be formed on the package ends, and one or more longitudinal leakage paths to remain between the package interior and one or both outer ends of the package.
For many packaged articles, minor remaining package end leak passages are not critical. However, as to other articles, such as medical products for example, even relatively minor package end leakage paths are highly indesirable. To this end, it is now common practice to configure the meshing outer ends of the combination sealing and cutting bars in a manner such that the ridges and valleys of the corrugated package end seal areas extend transversely to the package lengths. While this transverse sealing scheme represents an improvement over longitudinally extending seal corrugations, minor package end leaks can still, and often do, occur.
In view of the foregoing, it can be seen that a need exists for improved apparatus, and associated methods, for producing still better end seals on individual packages discharged from horizontal wrapping machines and the like. It is accordingly an object of the present invention to provide such improved apparatus and methods.